The internet is decentralized. It is literally millions of computers all around the world, no central point of failure. Google, Amazon and Facebook do not control the internet, if that is the extent of your internet usage, I feel sorry that you are missing out on so much more. If those companies were gone tomorrow, the internet would be just fine.
Bitcoin is decentralized, with many nodes holding a copy of the blockchain, no central point of failure.
By your logic, you may as well call it centralized since it only available in one galaxy, so if you can spread to more galaxies, then it will be more decentralized lol.
I think there is only a misinterpretation regarding with internet. First, let us first define what is internet? In my own understanding, it is a place where data stored and shared by millions of computers and gadgets all over the world. How come it will be centralized if people can modify or change something in internet. Maybe, there is some manipulation in other social media networks but there is always so called decentralization. Therefore, bitcoin can have it also since it is connected in internet.
I just want to correct one information here, we cannot store data on the internet, internet is the network that connects computers around the wotld, data is then stored to hard drives and data servers offered by different companies. Internet is just merely the platform for connection and it is considered decentralized as no one is owning the internet where cryptocurrency is working. Thus nodes and storages are also stored in different storage in different data servers.